Note 2 - Summary of Significant Accounting Policies (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)
Number of Reportable Segments	1
Advertising Expense	$ 34.3	$ 28.6	$ 25.3
Accounting Standards Update 2016-02 [Member]
Operating and Finance Lease, Right-of-Use Asset				$ 14.9
Operating and Finance Lease, Liability				$ 13.3
Franchise [Member]
Cost of Goods and Services Sold, Total	$ 22.7	$ 16.1	$ 15.7